Heat Pump

ABSTRACT

A heat pump system including a water reservoir tank, positioned proximate to a building, having a remote heat source associated therewith and ducting for drawing the heat source to the tank. The tank has an evaporator and a fan positioned to draw heat from the heat source and transfer the heat to the evaporator and a compressor for transferring the heat to the tank. A smart controller designed to optimize the efficiency of the heat pump water heaters may be used. The controller uses various inputs including ambient conditions and water consumption data to make an intelligent decision on when to run the system, based on a set of user preferences.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority from Australian Provisional Patent Application Nos 2010904258, 2011900535 and 2011901897 the contents of which are incorporated herein by reference.

INTRODUCTION TO THE INVENTION

The invention is the field of heat pumps, and in particular relates to a heat pump system adapted to efficiently utilise available heat sources.

BACKGROUND TO THE INVENTION

Heat pumps are most widely utilised for space heating and space cooling (often referred to as reverse cycle or split system air conditioners) or for heating water. Heat pumps are widely used in both domestic and industrial applications.

Heat pumps are utilised reasonably successfully worldwide to heat air, cool air and heat water. There are however a number of key limitations associated with heat pumps. Despite being a relatively efficient source of heat exchange they still consume a significant amount of energy. For example, space heating, cooling and hot water collectively account for 60-75% of all domestic energy use in Australia. With the rising energy prices and concern about global warming induced by greenhouse gas emissions there is a strong and growing demand for even lower energy space heating, cooling and hot water systems. The efficiency of heat pumps, as defined by the Co-efficient Of Performance (COP) is typically around 3-5, meaning that for every unit of energy (electricity) consumed 3-5 units of heating or cooling can be delivered.

Air source heat pumps, despite having undergone significant improvements in their operating efficiency, operate at the mercy of the available source air temperature. The efficiency of the Heat Pump reduces as the air source temperature drops. Current commercial air source heat pumps become unviable as the air temperature approaches zero. This is due to two effects, firstly the evaporator to condenser temperature differential becomes too high and secondly, icing occurs at the evaporator due to the extraction of atmospheric moisture onto a sub-zero heat exchanger. Once the evaporator is choked by ice it can no longer function and the heat pump efficiency will drop to near zero.

Air source heat pumps are increasingly being used for water heating to replace the less efficient element-type electric water heaters where the heat pump may be most favourably used during the off-peak electricity tariff interval. Unfortunately, this may provide a worst case operating scenario for a heat pump. The off peak tariff usually occurs late at night when the outside air temperature is at its lowest. In temperate regions it is common for the air temperature to drop to zero or below at night. Additionally, the hot water must be heated above 60° C., requiring a very high evaporator to condenser temperature differential. Even though the advertised COP of a heat pump may be between 3 and 5, on a cold night the typical observed performance is likely to drop below 2 and where icing occurs the total cycle COP may drop below 1 resulting in performance that is even worse than the electric element heater is was designed to replace.

An additional and independent issue related to heat pumps is that they emit compressor and fan noise. Heat pumps are typically located outside and this noise can adversely impact on home owners and their neighbours, particularly in high density living arrangements. A significant part of this problem is the time when the heat pump operates—typically associated with peak hot water usage being either in the morning or in the evening. Both of these times can cause problems. For example, if a person showers in the evening a heat pump may kick in and run for 3 or more hours, making noise at a time when residents may be attempting to go to sleep.

To date, the prior art systems typically place a simple on/off timer between the heat pump and the power source. However, such prior art solutions only allow for management of time of operation, it has no knowledge of how much hot water is in the tank, the users typical or current consumption patterns, air source temperature, electricity tariffs etc. Furthermore, using such prior art systems, it is possible for the user to run out of hot water. Moreover, such prior art systems determine a preset daily heating regime and do NOT allow for any dynamic decision making. The key advantage of such prior art is that it is simple to install and low cost.

Additionally, there are users who wish to operate their heat pump to optimise performance based on different personal needs and priorities. Such preferences may be to consume minimum energy, to operate at lowest cost, to provide the greatest system capacity or to operate most quietly at certain times of the day or night. There are currently no heat pumps on the market that offer this level of flexibility.

Air source heat pump manufacturers have been working for many years to incrementally improve the performance and efficiency of heat pumps with various innovations. In particular more efficient compressors, heat exchangers and alternative refrigerants have been utilised to incrementally improve heat pump performance, including improving efficiency under unfavourable conditions.

Split systems with larger free standing evaporators have improved the heat extraction performance and allow reasonably efficient operation down to temperatures near zero centigrade. Improvements to de-icing algorithms and mechanisms allow heat pumps to recover from icing conditions and shut down under conditions where the heat pump efficiency has dropped to an unacceptable level.

Manufacturers are aware of the limitations of system performance in low temperature conditions and often include installation recommendations to place the evaporator in a location to maximize available warmth, for example placement to gain maximum exposure to the sun and in a location with good airflow to avoid frost.

An alternative to the air source heat pump in areas with very low air temperatures is the ground source heat pump or geothermal heat pump. This type of system is very expensive to install and is most suited to cold climates where geothermal heat energy is readily available. These are not switchable or selective systems but rely on a renewable source of geothermal energy to maintain the evaporator temperature.

Another alternative to the air source heat pump is the solar assisted heat pump where the evaporator is integrated to a solar thermal panel typically mounted on the roof This type of system provides excellent performance when the sun is shining but operation is very inefficient on cold nights and is therefore not suited to off-peak operation.

Recent developments with heat pumps have seen them more widely adopted for domestic water heating applications. Previously the high cost, low reliability and low efficiency of heat pumps has precluded them from competing against conventional electric water heaters and gas water heaters. The current developments include attempts to solve the problem of diminished heat source availability and incorporate some of the following:

-   1. Adding de-icing features to allow the air source heat pump to     continue to operate but at much lower efficiency; -   2. Increasing the size of the evaporator to harvest a smaller amount     of energy from a larger amount of heat source. Here the heat pump     continues to operate but again at lower efficiency; -   3. Placing the evaporator in a roof mounted solar collector to     directly extract heat from the sun. This provides excellent daytime     performance but is unsuitable for off-peak night time operation; -   4. Retrieve the heat from a “renewable” source such as the ground.     This is very expensive, only suitable for some geographic areas and     falls outside the realm of air sourced heat pumps.

However, notwithstanding the current developments, none of the available heat pump systems provide a configuration combining ease of installation and access to optimal input air supplies.

One object of the invention is to provide an improved heat pump adapted to efficiently utilise a range of available heat sources.

In a conventional heat pump the system runs based on the temperature of water in the tank, which is influenced mostly by when the water is used (and therefore replaced with cold water) or ambient heat losses.

In a typical domestic situation the time that the heat pump runs is not well aligned with when the heat pump should run to minimise either energy use or energy costs. For example, if a person has a shower at 7 a.m. then the heat pump will typically kick in at that time. This is often the coldest part of the day. If the system was to wait until mid-day to reheat the tank then the energy consumed may be reduced by up to 50%, depending on ambient conditions.

There exists a number of prior art appliance control devices to manage energy consumption with respect to prevailing electricity tariffs. The off-peak meter and associated timer or network control being the preferred method of heating water during the lowest tariff period. When combined with a suitable thermostat such prior art systems are ideal for resistive element electric water heaters. However, for the control of heat-pumps, the off-peak period often coincides with the lowest prevailing temperatures ie: during the early morning (12 a.m.-6 a.m.). When a heat pump will consume more energy and in cold climates could cost more to run than if operating outside the off-peak interval.

Furthermore, with an increasing prevalence of ‘smart meters’ and Time-Of-Use (TOU) electricity tariffs we are seeing an increase in the variation in electricity prices throughout the day. In an ideal world a heat pump hot water system would not run during a period of peak electricity tariff in order to both minimise the cost to the consumer and to minimise the load on the electricity network during peak periods.

Demand side energy management devices can also be used to control the time of operation of a heat-pump, or any other energy consuming device. These prior art devices are typically used to load-shed during peak consumption (and therefore tariff) intervals and have no knowledge of water consumption or tank capacity and therefore cut the power independent of the need to reheat the water storage.

STATEMENTS OF THE INVENTION

In a first aspect the invention provides a heat pump system for moving thermal energy between a heat source and a heat sink, comprising a condenser and an evaporator communicating via a refrigerant driven through said condenser and evaporator via a compressor wherein said evaporator absorbs heat from said heat source and the condenser loses heat to said heat sink characterised in that said system includes access to a heat source remote from said system.

The system of the invention is preferably adapted for installation to a building structure with the heat source being accessed from the roof cavity of the building structure.

The system of the invention preferably include a water reservoir tank as the heat sink. The system most preferably positions the evaporator at or near the top of the tank with the system preferably including ducting for communicating with said roof cavity heat source to the evaporator.

The system of the invention preferably includes a fan means adapted to draw air from the roof cavity via the ducting to the evaporator with the fan means most preferably being positioned in close proximity to the evaporator. The fan is most preferably a centrifugal fan or similar fan design, being specifically adapted to draw air from the remote source via a length of ducting with the design of the fan, particularly adapted to accommodate any increase the pressure drop as a result of drawing the air from the remote source. The positioning and configuration of the ducting evaporator and fan, at or near the top of the tank, allows for the close juxtaposition of the components of the system associated with the evaporator, thereby minimising refrigeration plumbing lines and other complications, and also positioning the components of light physical weight, at or near the top of the water tank, so as to maximise the physical stability of the system. In a particularly preferred embodiment, the more heavy elements of the system including the compressor, are most preferably positioned at or near the base of the tank in order to maximise the lowering of the centre of gravity of the system as a whole.

In another aspect the invention provides a heat pump kit comprising the system as previously described, what the kit including the following elements:

a) a water reservoir tank adapted for positioning under the eaves of a building structure having a roof cavity to act as a remote heat source;

b) an evaporated position for fitting at or near the top of said tank;

c) a fan positioned at or near the top of said tank to draw air to seek compressor;

d) ducting for communicating with said roof cavity and accessing air from within said cavity;

In another aspect the invention provides a heat pump system for moving thermal energy between a heat source and a heat sink comprising a condenser and an evaporator communicating via a refrigerant driven through said condenser and evaporator via a compressor wherein the evaporator absorbs heat from said heat source and the condenser looses heat to said heat sink characterised in that said system includes access to two or more heat sources and a controller adapted to select from said available heat sources and or the ability to optimise the efficiency of said heat pump.

The two or more heat sources may include heat sources at different physical locations or a single heat source accessed at different times of the day.

The system may include access to two or more heat sinks and a controller adapted to select from said heat sinks.

The controller may be adapted to select from a single heat source and identify the optimum time of day to draw heat.

The controller preferably includes the ability to select both heat sources and heat sinks.

The controller preferably includes programming to choose optimisation modes selected from highest efficiency, lowest cost, quietest operation and/or highest capacity.

In one particular embodiment the heat source may be chosen by strategic placement of said evaporator and the heat sink chosen by strategic placement of said condenser.

In another embodiment the heat source is a roof cavity with the controller selecting the optimum time of day when the roof cavity is warmest to draw heat.

In another aspect the invention provides a heat pump system for moving thermal energy between a heat source and a heat sink comprising a condenser and an evaporator communicating via a refrigerant driver through said condenser and evaporator via a compressor wherein said evaporator absorbs heat from said heat source and said compressor looses heat to said heat sink characterised in that said system physically separates said compressor from said evaporator and includes access for said separated evaporator to two or more heat sources and a controller adapted to select from said available heat sources to optimise the efficiency of said heat pump.

In another aspect the invention provides a controller for regulating the output power supply to a heat pump said controller comprising an output power supply for said heat pump, a range of input sources for providing data selected from any one or a combination of:

-   -   atmospheric conditions     -   heat pump conditions     -   output power supplier data     -   historical use data     -   user direct input         and a means for analysing said data, wherein said analysing         means is adapted to determine the most favourable outcome based         on user defined preference.

In another aspect the invention provides a hot water control system, comprising a reservoir for hot water storage, a heat pump as the primary source of heating for said water, and a controller as previously described.

In a particularly preferred embodiment, the input sources may include any one or a combination of the following:

-   -   source air temperature     -   water storage temperature     -   source air humidity     -   source water temperature     -   source water flow rate     -   mains current electricity used by the heat pump     -   electricity tariff data     -   time of day     -   smart meter interface.

The control system most preferably as a user defined preference has the energy efficiency of the system. Alternatively, the user defined preference may be the cost efficiency of the system, or the hot water capacity of the system, or the time of operation of the system.

In a particularly preferred embodiment, the user may override the system as previously described completely by bypassing the controller.

In a particularly preferred aspect, the hot water control system as previously described may further comprise a processor and a data storage unit, wherein the controller main monitor user behaviour and adapt to the individual user preferences.

In a particularly preferred embodiment, the hot water control system as previously described may further comprise a smart meter, wherein the controller has the ability to communicate with the electricity grid to monitor demands, tariffs and adjust regulation of the heat pump accordingly.

The invention will now be described with reference to the particularly preferred embodiment given in the following examples and general description with reference to the figures.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE ONE

Referring firstly to FIG. 1, a particularly preferred embodiment of the invention is shown in schematic form in the form of a heat pump system particularly adapted for heating domestic hot water, utilising the heat from the roof cavity of a domestic dwelling.

The heat pump system includes a primary water reservoir tank 1, which functions as a heat sink. The water tank is configured for placement on the ground proximate to the dwelling 2. The heat pump system is specifically configured to a place all the lightweight elements and components toward the top of the tank 1 and the heavier components towards the bottom of the tank 1 in order to maximise stability and ease of fitting to the dwelling 2. The evaporator or evaporators 3 constitute one of the lighter weight components of the system and are conveniently placed on top of the tank and are adapted to receive air flow from the roof cavity 4, which provides air that is heated by virtue of the relationship to the dwelling 2, relative to the available outside air. The heat pump system of this embodiment draws air directly from the roof cavity 4 by way of ducting 5 with the air being drawn to the evaporator by virtue of a fan 6 positioned in close proximity to the evaporator 3 on top of the tank 1. The fan is most preferably of a centrifugal or similar type with the ability to draw large volumes of air over a considerable distance with minimal pressure drop. The compressor 7 is used to compress and heat refrigerant which then runs through a condenser thereby providing heat to the water. The compressor is positioned toward the bottom of the tank 1 being a generally heavy component. The position of the compressor near the base of the tank increases the physical stability of a system as a whole.

In this manner, the heat pump system of the invention provides a highly compact system, with all the major operating components located in direct cooperation and thereby requiring only the installation of ducting 5, to the roof cavity 4 in order for the system to draw a supply of preheated air to service the heat pump.

In another embodiment of the invention shown in FIGS. 2 and 3, the heat pump system of the invention uses a variety of inputs including the optional use of the input of a dwelling roof cavity as previously described and outputs to control the timing and heat transfer routing between various components of the system. The timing and routing are dynamically controlled to achieve the selected performance benefits, which can be chosen from:

a) Minimise total system energy consumption

b) Minimise total operating cost

c) Maximise total system capacity

d) Minimise disturbance due to operating noise

The invention provides a means whereby the operating efficiency of an existing heat pump can be significantly improved by providing it with a more favourable operating environment and as a result, improving its performance. Additionally the invention allows for the harvest of the otherwise wasted exhaust from the heat pump to use for cooling applications.

The invention allows two or more heat sources 4 to be selectively managed to provide the heat pump 8 with the best evaporator heat extraction source. Examples of heat sources are the outside air (conventional heat source), the air in the roof cavity 4 of a building 2 and the output of a solar thermal air heater.

A further example of multiple heat sources is the apparatus to select between roof cavity air, air from a solar thermal collector or outside ambient air. Although in one embodiment these air sources are all sampled from within the roof cavity, the use of supplementary dampers, valves and/or fans determines which source provides the greatest heat availability.

In another aspect the invention then allows the output from the evaporator 3 to be selectively redirected when a cooling function is required. Examples of a cooling function can be living space cooling. This re-use of cooled air is of benefit when the lowest energy consumption is selected as it can save the need for an additional air conditioning device whose heat output would otherwise be wasted.

The invention provides a heat pump controller that has two or more inputs representing the temperature of each available heat source, an optional input to indicate the availability of off peak electricity and an optional input representing the internal living space temperature. The controller's outputs include switchable power to the heat pump, control of fans, dampers or valves to manage air source flow and optional pumps and valves to manage switching between evaporator circuits.

The invention differs from previous attempts to improve heat pump efficiency where the controller makes dynamic decisions about operational timing and heat source/discharge routing based on high level goals determined by the operator. The system can be arbitrarily programmed to optimize one or more of lowest cost operation, greatest energy efficiency, highest system capacity or quietest operation.

For example, the use of a solar thermal booster and roof cavity air source allows for dramatically improved daytime operation that can be traded against the benefits of night-time off peak operation. Thus if the operator elects a lowest cost mode of operation then the controller may opt to heat the water during a peak tariff interval due to the very high efficiency resulting in much shorter operation, lower power consumption and overall lower cost.

Another example is the use of cooled exhaust air for living space cooling. In summer when the living space rises about a user defined set point the system can elect to operate at a peak tariff based on the net benefit of providing cool air while heating the water. Otherwise an alternative air conditioning device may have been used with the waste heat exhausted to the atmosphere. The system is therefore using the lowest amount of energy to provide the greatest system capacity at possibly also the lowest cost of operation when savings on alternative cooling are taken into account.

In this embodiment of the invention, rather than using a single, static heat source, such as the air surrounding a ground based heat pump air exchanger or over the roof cavity of a dwelling as previously described; the heat pump system of the invention may offer a selection of heat sources that can be opportunistically utilized for maximum heat pump efficiency.

Additionally rather than the heat pump operating during a fixed period at a preset time each day, this embodiment of the invention allows the heat pump to operate at a time when the greatest total benefit can be attained. The operator can select the nature of the maximum benefit in terms of operating cost, energy consumption, greatest system capacity or a combination of these.

The essence of the solution to improving existing heat-pump efficiency is to have two or more selectable evaporator heat sources and sufficient temperature data to be able to select the most appropriate source at the most appropriate interval that will provide highest operating efficiency or greatest total system energy utilization. Further, the switching algorithm takes into account the time of operation (for off-peak electricity), the need for cooled exhaust air (space cooling) and the need for hot water. In one embodiment the invention may include:

-   -   Two or more heat sources that can be routed to one or more         evaporator circuits on a heat pump;     -   A temperature sensor for each heat source;     -   A water storage tank coupled to the heat pump condenser;     -   A temperature sensor in the water storage tank;     -   A control module embodying the selection algorithm with the         ability to select between heat sources and switch power to the         compressor and fans.         Additionally the control algorithm has the following data preset         or adjustable:

-   The desired hot water storage temperature (hot water thermostat set     point).     For off-peak electricity use the following additional features are     required:     -   The control module fitted with either a real time clock with         off-peak operating times or an off-peak power circuit routed to         the control module or an input (wired or data) that is activated         during off-peak intervals;     -   The cost of both peak and off-peak electricity are optionally         stored on the controller;     -   The COP vs. Evaporator/Condenser temperature curve is stored on         the controller.         For the space cooling feature the following additional features         are required:     -   A duct with selectable damper and/or switchable fan to transfer         exhaust air from the evaporator to the living space;         Additionally the control algorithm has the following data preset         or adjustable:     -   The desired living space temperature (room thermostat set         point).

In the embodiments, described an alternative to avoid mounting the heat-pump (compressor and evaporator) in the roof cavity is to move the system outside the building, for example under eaves, or mounted at ground level. An additional duct is then required to exact air from the heated space, being the roof cavity or other internal space. The exhaust air is then able to be freely discharged to the surroundings. However to utilise the space cooling feature a switchable return duct would then be required to take the cooled exhaust air back to the living space when a cooling function is required.

Another alternative is to remove the air heat recovery ducting and implement the system switching between two evaporator circuits, one on external ambient air as per a conventional heat exchanger and the other in a swimming pool water circuit as described in example seven. This simpler system then only has a choice of two heat sources but will still provide performance benefits on very cold nights when the ambient air is too cold for satisfactory operation. Such a system is best coupled to a solar pool heater and pool blanket to maximise the performance benefit.

The key advantages of this system are:

-   1. Lower energy use to provide a given quantity of heat or hot water     than a conventional air source heat pump; -   2. Ability to viably operate an air source heat pump year round in     temperate regions that experience periods of very low air     temperature; -   3. Ability to utilise the cool air discharge from a heat pump for     gainful purposes such as home cooling in summer The cool air is     otherwise wasted on existing systems; -   4. Ability to control the heat pump duty cycle depending on the     daily temperature cycle for optimal performance; -   5. Ability to interface with smart meters to reduce the cost of     running the system.

EXAMPLE TWO

Referring now to FIG. 3, another embodiment of the invention, includes the physical separation of the heat pump 8 by separation of the compressor 7 and evaporator 3, thereby allowing ready positioning of the evaporator close to the preferred heat source, whilst involving minimal disruption to conventional building and installation procedures.

Whilst the previous examples exhibit substantial merit over prior art known, two disadvantages may occur in certain circumstances. For example, it can be difficult to install the heat pump embodiment as shown in FIG. 2, to a single story house without eaves or alternatively, to a multi-story building. In another example, such installations as shown in FIG. 2 may be regarded as aesthetically undesirable, due to the ducting required for retro-fitting to the side of the dwelling in question.

In order to address these issues, the invention as previously described has been modified with the provision of the heat pump into the roof space or by direct mounting onto the eaves of a dwelling. Whilst such a modification is satisfactory, the heat pump as a complete unit can be quite cumbersome and physically heavy and therefore difficult to move and install in the roof of a dwelling or onto an eave. In order to address the shortcomings, one embodiment of the invention has been modified by the physical separation of the heat pump into two key components, being the compressor and the evaporator.

Accordingly, in this particularly preferred aspect of the invention, the evaporator component of the heat pump is available for drawing heat from a heat source, selected from the roof cavity of a dwelling whilst the compressor component of the heat pump remains positioned on or near ground level. In this manner, the heavy or cumbersome elements of the heat pump remain at ground level, whilst the evaporator and key elements responsible for heat absorption can be readily placed in the roof cavity, with minimal disruption due to its lightweight and small size and connected to the compressor by slimline piping or conduiting with minimal aesthetic or physical disruption to the exterior of a dwelling.

In this particular embodiment of the invention, the separating of the system allows the evaporator to be placed in a wide range of orientations or positions, dependent on the construction of a building in question. For example, the evaporator can be mounted in a roof cavity, as a physical part of the roof, for example including a skylight, in the eaves or any other warm space, for example against a chimney

In situations where the provision of the evaporator inside the roof cavity, thereby enabling a smart controller to work whilst being practical for a plumber to install, may potentially involve some performance issues in certain circumstances. For example, if the roof space in question is small and includes a very well sealed cavity, the cool air discharge from the evaporator could potentially over-cool the roof space, thereby lowering the performance of the system dramatically. Whilst this is not an issue on almost all rooves that have very large thermal masses, there is a potential issue on some situations with smaller flat roofed houses with small sealed and insulated roof cavities. In these instances, the embodiment of the invention could be adapted by discharging the cold air of the evaporator out of the roof cavity. Such a discharge could be affected by way of a vent in the roof per se, or a vent through the eaves.

In respect to the specific challenges detailed above, the invention may provide a low profile evaporator adapted for mounting directly onto the eaves. In this embodiment, air would be drawn from the roof cavity through the evaporator and discharged out through the eaves. Such an embodiment would allow particular ease of installation as the lightweight evaporator can be fitted to the eaves in close proximity to the hot water tank, with no need for the installer to enter the roof cavity and cause potential interruption to the interior of the roof.

EXAMPLE THREE

In another example of the invention the hardware of a conventional heat pump driven hot water system is used where the evaporator is mounted remotely from the tank inside the roof cavity of a home. In this example there is no ducting applied to the evaporator—which sits inside the roof cavity. The smart controller is programmed to operate the system when the roof cavity is warmest which dramatically improves the efficiency of the heat pump compared to a situation where the evaporator is outside on the ground.

Multiple (e.g. 2 or 3) temperature sensors are installed inside the water tank to allow the smart controller to monitor how much hot water has been used. These sensors will sense the amount of hot water remaining in the tank (high, low and very low). If hot water is used during the day and the amount of hot water drops below the “high” level then the smart controller will automatically start the heat pump and ensure the tank is completely full of hot water by the end of the warmest ambient conditions. If hot water is consumed in the evening or night when the roof cavity is cold then the smart controller will deliberately not start the heat pump until there is either a very low hot water supply or the sun comes up the next day and the roof cavity starts warming up.

There is no difference between summer and winter operation. In both cases the heat is extracted from the roof cavity, or in other words the roof cavity is cooled. In summer this has the impact of reducing unwanted heat transfer from the roof space to the home. The benefits of this system are greatly reduced energy consumption to heat hot water.

EXAMPLE FOUR

The embodiment given here is similar to Example three, except the air leaving the evaporator (mounted in the roof cavity) is sent via a 2-way diverter valve. In winter the cold air leaving the evaporator is ducted outside the roof through either the eaves or a roof-mounted vent. In summer the cold air is ducted into the house. The control system outlined in example one is still the same, the only addition is the two way valve to direct the air flow.

The control system will also have some user programmable options to select the time of operation. For example on a hot summer day the roof cavity may be above 50° C. from 10:00 a.m. in the morning until 6:00 p.m. at night. Therefore there is plenty of time to heat the hot water during the day. The user may select the system to deliberately heat the water between 4.00 p.m. and 6.00 p.m. so that the free cool air is used to cool the home prior to the home owners arriving home from work.

EXAMPLE FIVE

The embodiment provided is similar to Example Three except the temperature of the roof cavity is boosted by adding a solar air heating panel, to the roof Air from the solar air heating panel is ducted directly into the roof cavity to make it even warmer, so that the heat pump performance is further improved.

EXAMPLE SIX

The embodiment provided is similar to Example Four. Instead of just heating hot water for a domestic hot water needs (often a 200 to 300 litre tank), a swimming pool or spa bath may also be heated (can be thousands of litres). Therefore a great deal more heat energy is required to heat the much larger volume of water, albeit to a lower temperature.

The control system is adapted to heat the hot water only, or both and may be user selectable. Hot water for showers etc is required all year round; however, the spa or pool is only required to be heated at certain times of year. Depending on the climate region which may be summer, or the shoulder seasons when the pool is not quite warm enough (spring and autumn) In other situations a spa bath may be required to be heated in winter on occasion.

A diverter valve will be included to allow heat to be directed to either the hot water tank or the spa. A separate heat exchanger may be required for the spa—e.g. a small circulating pump circulates water from the spa to the heat pump heat exchanger and back to the spa. Water from the spa must not contaminate the hot water system so this must be a completely separate water circuit, however it could use a common heat exchanger.

The controller may heat the domestic hot water first (when the roof cavity is warm) then switch to the pool or spa. The pool or spa may be “opportunistically” heated—ie heated when conditions are favourable. This is similar to conventional solar pool heaters which only circulate water through the black pipes on a roof when they are hot. Moreover, there is a lot more water to heat, so therefore there is a lot more cool air given off. It is therefore preferred that in winter all the cold air is ducted out of the roof cavity (or it risks becoming very cold and inefficient). In summer there is an opportunity to provide ample air conditioning for the entire home. The control system may switch from heating mode to cooling mode; i.e. instead of heating the pool and opportunistically cooling the home, the controller may be programmed to cool the home and opportunistically heating the pool. This flip in operating mode will only be possibly if a large volume of water is available to heat, otherwise the pool water would get too warm. In both scenarios the smart controller will need user settings allowing it to stop if either the pool gets too warm or the house gets too cold.

EXAMPLE SEVEN

In this embodiment the heat pump is not located in the roof cavity, it is located outside like a conventional system. The evaporator has the ability to source its heat from either water or air via a dual-flow heat exchanger.

The heat pump is used for both heating and cooling the home and heating (or cooling) the pool. It is essential to have a pool or large body of water in this scenario. There are multiple operating modes:

-   -   a) In home-heating mode the system draws its heat from outside         air, exactly like a conventional system, during the day;     -   b) At night in home-heating mode the system would become very         inefficient if it sourced its heat from the air (which is         obviously cold), so it switches to source its heat from the         water source such as the pool. In winter this has the effect of         cooling the pool water. A side benefit of extracting heat from         an unused swimming pool in winter is that the maintenance cost         of the pool is reduced as the need for chemical additives         decreases as the average temperature of the pool decreases;     -   c) In summer the system cools the home and dumps its heat to the         outside air at night (eg on a relatively cool summer night);     -   d) During the day in summer the system will sense that the         outside air temperature is very warm and so will switch to         dumping its heat into the pool. This is more efficient as an air         conditioner for the home, but it also has the side-effect of         warming the pool;     -   e) The smart controller needs to make intelligent decisions         about when to source from air or pool. If for example the pool         reaches a preset threshold then it would need to stop heating         the pool or it will become too warm. Similarly if the pool         becomes too cold in winter then there is a risk it could freeze         in some climates so this needs to be managed.         The key features of the invention that distinguish this example         prior art are:

-   1. The user has be ability to set operation based on any the     following criteria selected in order of importance:     -   a) Minimise total system energy consumption     -   b) Minimise total operating cost     -   c) Maximise total system capacity     -   d) Minimise disturbance due to operating noise

The user has the opportunity to change their priorities giving the system unprecedented flexibility to operate in a fashion optimally aligned to user preferences. One practical advantage is that the user may choose to save money on operating costs during spring and autumn but may give priority to living space comfort in the hotter summer months.

-   2. Automatic selection of operating interval based on high level     user objectives. The timing of the heat pumps operation is governed     by a calculation of efficiency, cost of electricity and ambient     living space conditions. The system will operate when conditions     most closely match the criteria selected by the user. The practical     advantage of this is exemplified by the automated decision to     operate during night time off-peak to save money for most of the     year but on very hot days the system will operate to cool the house     while still achieving low cost due to the high efficiency possible     when the air source is very warm. -   3. Dynamic selection of the heat pump evaporator energy source where     two or more heat sources can be selectively harvested. To meet the     selected operating criteria the heat pump can switch between     evaporator energy sources. Examples of the practical benefits     include choosing the warmest energy source to maximize efficiency,     choosing a pool water heat exchanger instead of an air exchanger at     night to reduce operating noise or switching from one source to     another during operation such as when the warmed roof cavity air has     been exhausted, switching to a pool water heat exchanger. -   4. Utilising the waste “cool” energy from a heat pump that is used     to heat water to cool the building in summer This cool energy may be     used to cool either the roof cavity or the building itself. -   5. Ability to selectively harvest energy from a swimming pool. This     feature allows the system to meet a low noise criteria as well as     operate with improved efficiency at times when the ambient air     temperature is too low for normal heat pump operation. -   6. Locating the heat pump evaporator in the roof cavity is a simple     and low cost method to both extract the heat but also to deliver the     cool air to the home via diffusers in the ceiling.

EXAMPLE EIGHT

In another embodiment of the invention, the two or more heat sources refer to a single physical source of heat being the roof cavity of a house where air is drawn from the cavity at specific times of the day so as to maximise this source of warm air during optimum times of the day.

In this embodiment of the invention the Example is supported by the following figures:

FIG. 2 shows a schematic representation of a preferred implementation of the invention in front and side view.

FIG. 4 shows the current operating conditions of prior art systems.

FIG. 5 shows the operating conditions of this particular embodiment of the invention.

FIG. 6 shows the opportunity for performance improvement with the invention.

FIG. 7 shows a summary of energy consumption findings using the invention.

FIG. 8 shows predicted performance improvements of the current invention.

Referring to FIG. 2, a schematic representation of this particular embodiment of the invention is shown where warm air is drawn from the roof cavity 4 via suitable ducting 5 connected to the outside of the house 2 and communicating with the roof cavity. The ducting draws the warm air to a heat pump 8 located in close proximity to the ducting with the hot water then being transferred to a storage tank 1. Waste air is discharged to the outside atmosphere thereby serving an additional function of reducing unwanted hot air in the roof cavity of the house.

The warm air drawn from the roof cavity significantly boosts the performance of the hot water heat pump compared to air being drawn from the ambient atmosphere with improvements in the order of 20% to 45% as is shown in FIGS. 4 through to 6.

In this particular embodiment of the invention, there is no need for a mechanism to select from air sources and therefore this embodiment provides a highly simplified version of the invention. The air is always drawn from one source being the roof cavity, because the air in a roof cavity is always either warmer than ambient air or the same as ambient air. As the heat value of air in the roof cavity is never less than ambient air, there is no need to have any valve or switching arrangements which highly simplifies this particular embodiment of the invention.

In this particular embodiment of the invention, most preferably will include a smart controller used to identify the optimum time of date to run the system and draw warm air from the roof cavity when that air is at its warmest and able to provide the most efficient source for the heat pump. The controller may also take into account hot water demand and potential user input in accordance with the time of day and may also take into account energy prices to determine the optimum duty cycle.

EXAMPLE NINE

In this embodiment the invention provides a smart controller for a heat pump hot water system. It is suitable for retro fit add-on to existing commercial heat pumps or OEM integration with new heat pumps.

The controller switches the power to a conventional air-source heat pump. By controlling the availability of power to the pump the system can control the time and duration of operation.

The controller uses a number of inputs and custom algorithms to determine the optimal time and duration for running the heat pump. These inputs include:

A Air source temperature B Hot water tank temperature C Air source humidity [optional] D Water source temperature [optional] E Water source flow rate [optional] F Mains current used by the heat pump [optional] G Electricity tariff data (eg a table) [optional] H Time of day (24 hr clock) I Smart meter connection interface [optional]

FIGS. 10 and 11 outline a hardware schematic of the electronics board.

Based on the prevailing atmospheric conditions, residual hot water capacity and historical data, the invention determines the most efficient time to operate the heat-pump and can delay re-heating until that time arrives. This is termed the “lowest energy mode”.

FIGS. 12 through 16 outline the algorithms used by said hardware to make decisions on when to operate.

FIG. 9 outlines a minimum embodiment of the invention.

If time-of-day data is available the invention can further schedule reheating to avoid periods where noise is unfavourable or some other reason is scheduled to lock-out operation.

If tariff data is available the invention can further schedule reheating to avoid periods where high tariffs occur. In this mode the “most efficient time” of operation can be determined as the lowest cost time of operation. This is termed the “lowest cost mode”.

Furthermore reheating may be scheduled based on prevailing regulatory requirements for storage hot water systems. i.e.: The periodic heating of water above a pre-determined minimum temperature to inhibit bacterial growth in the storage tank.

The reheating of the water storage will always be scheduled prior to the residual hot water capacity falling below a pre-determined minimum. To do this the residual capacity is modelled into the future to determine the latest possible time for re-heating. The controller has the ability to defer operation if suitable conditions are not available. Conventional heat pumps turn on at predetermined time or temperature and will continue to operate until their heating objective has been met. In cold weather this can result in prolonged operation under conditions of very low efficiency. The controller to calculate the operating COP and defer operation until more favourable conditions are available.

The predictive behaviour of the controller may cause the heat-pump to operate outside the period deemed most favourable in terms of efficiency or cost. This can occur when:

1. The most favourable period is locked-out for reasons of noise or similar

2. The residual capacity will be exhausted before the most favourable period arrives

3. The period of highest efficiency occurs during a period of high tariffs (lowest cost mode)

4. The period of lowest tariff occurs during a period of low efficiency (lowest energy mode)

Once the heat-pump has commenced a reheating cycle it is possible for the controller to terminate the reheat in the event that more favourable conditions are expected. This can occur when:

1. The residual capacity has risen to an acceptable level;

2. Regulatory reheating requirements have been satisfied;

3. Ambient conditions deteriorate such that better conditions are likely if reheating is deferred.

Residual hot water capacity is defined as the volume of water in the storage tank at, or above, a predetermined minimum acceptable temperature.

Residual hot water capacity can be determined in several ways:

1. Have sufficient temperature sensors in the tank to approximate the water temperature profile and then, given a knowledge of the tank geometry, determine the residual capacity; or

2. Have fewer temperature sensors in the tank and measure the volume of water being consumed and the temperature of the replacement water. Given knowledge of the tanks thermal profiling behavior it is possible to calculate the residual capacity; or

3. Measure only the inlet and outlet water temperatures, consumption flow rate and heat energy input. From this data it is possible to mathematically model the storage tank and thus derive the residual capacity.

The embodiment of the invention described uses option (2) above, but any of these approaches are suitable,

Future prediction of residual hot water capacity is done by learning daily consumption behaviour and then applying the expected consumption to the current residual capacity. Thus the future residual capacity can be predicted.

The minimum allowed residual capacity is determined by one of the following methods:

1. A fixed and predetermined volume based on tank capacity, expressed as either a percentage or absolute volume in litres.

2. A learned volume based on consumption behavior and expected reheating time.

The data relating to prevailing atmospheric conditions can be measured and stored in various forms. The basis of the ambient measurement is to determine the enthalpy of the air entering the heap pumps evaporator. This is a key determinant of heat pump efficiency.

Measurement of air temperature alone gives a reasonable approximation of enthalpy. The optional addition of humidity data increases the accuracy of the enthalpy data. Humidity can also be replaced by wet bulb temperature or dew point temperature in the acquired data.

The atmospheric data is ideally measured at the air source inlet of the evaporator, however any general ambient atmospheric measurement may be used, including data acquired remotely and transferred to the controller by electronic means.

Where the controller of the invention needs some form of historical data in order to compare current operation with expected operation at a future time, such historical data can be in many forms ranging from a simple daily average, through to complex daily, weekly or even annual data histograms.

The simplest form of historical data is the daily average temperature. This would allow operation to be deferred if the current temperature is below average. The system is then making the assumption that at some point in the future the temperature will rise above average and more favourable conditions will prevail.

In one preferred embodiment the historical data is a daily enthalpy histogram that learns ambient conditions and refines (averages) this data over a period of days or weeks. This provides a high quality prediction of expected conditions over the coming 24 hours or more.

The historic data is offset by currently observed conditions in a time decaying fashion. Thus short term fluctuations from normal conditions are taken into account. Alternately, historic data can be replaced by real time weather prediction data obtained via internet or network connection via a smart meter.

The key advantage of this particular embodiment of the invention system is a dramatic increase in the efficiency of any heat pump water heater. The prediction and behavioural monitoring algorithms behind the hardware enable the system to be bespoke to each household's water usage behaviour, optimising the system after a short amount of time to have maximum efficiency for each individual household. This behaviour is also completely dynamic, allowing for a sudden change in conditions to override any algorithm and for the system to turn on.

The commercial advantage of the system of the invention is decreased cost to run the system, which in turn decreases the payback period. This makes the product more appealing to the market as a whole. The invention also appeals to the market of the environmentally conscious, thanks to the user having the option of ignoring overall cost and tuning the system for minimal energy consumption.

The system of the invention has the ability to communicate with the electricity grid via smart meters which enables awareness of any changes in grid demand which potentially allows electricity providers to manage the load on the grid. The smart meter communication also allows real time input to the current and future tariff charge rates. It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. 

We claim:
 1. A heat pump system for moving thermal energy between a heat source and a heat sink, comprising a condenser and an evaporator communicating via a refrigerant driven through said condenser and evaporator via a compressor wherein said evaporator absorbs heat from said heat source and the condenser loses heat to said heat sink characterised in that said system includes access to a heat source remote from said system, said system is adapted for installation to a building structure and said heat source is the roof cavity of said building structure, wherein said system includes a water reservoir tank as said heat sink and said evaporator is positioned at or near the top of said tank and said system includes ducting communicating said evaporator with said roof cavity heat source. 2.-4. (canceled)
 5. A heat pump system according to claim 1, further including a fan means positioned to cooperate with said evaporator and adapted to draw air from said roof cavity to said evaporator via said ducting.
 6. A heat pump system according to claim 5, wherein said fan is a centrifugal fan or the like adapted to draw air from said remote source and accommodate any increased pressure drop.
 7. A heat pump system according to claim 1, wherein said compressor is positioned at or near the base of said tank.
 8. A heat pump kit comprising a system according to claim 1, wherein said kit includes: a) a water reservoir tank adapted for positioning under the eaves of a building structure having a roof cavity; b) an evaporator positioned for fitting at or near the top of said tank; c) a fan positioned at or near the top of said tank to draw air to said evaporator; d) ducting for communicating with said roof cavity and accessing air within said cavity.
 9. A heat pump system for moving thermal energy between a heat source and a heat sink, comprising a condenser and an evaporator communicating via a refrigerant driven through said condenser and evaporator via a compressor wherein the evaporator absorbs heat from said heat source and the condenser loses heat to said heat sink characterised in that said system includes access to two or more heat sources and a controller adapted to select from said available heat sources to optimise the efficiency of said heat pump, one or more of said heat sources are accessed remote from said system, said two or more heat sources include heat sources at different physical locations or a single heat source accessed at different times of the day, said heat pump system including access to two or more heat sinks and a controller adapted to select from said heat sinks and wherein said controller is adapted to select from a single heat source and identify the optimum time of day to draw heat. 10.-13. (canceled)
 14. A heat pump system according to claim 9, wherein said controller has the ability to select both heat sources and heat sinks.
 15. A heat pump system according to claim 9, wherein said controller includes programming to choose optimisation modes selected from highest efficiency, lowest cost, quietest operation and greatest capacity. 16.-17. (canceled)
 18. A controller for regulating the output power supply to a heat pump said controller comprising an output power supply for said heat pump, a range of input sources for providing data selected from any one or a combination of: atmospheric conditions; heat pump conditions; output power supplier data; historical use data; user direct input; and a means for analysing said data, wherein said analysing means is adapted to determine the most favourable outcome based on user defined preference.
 19. A hot water control system comprising a reservoir for water storage, a heat pump as the primary source of heating for said water and a controller according to claim
 18. 20. A control system according to claim 19, wherein said input sources include any one or a combination of: source air temperature; water storage temperature; source air humidity; source water temperature; source water flow rate; mains current electricity used by said heat pump; electricity tariff data; time of day; and smart meter interface.
 21. The hot water control system of claim 19, wherein the user defined preference is the energy-efficiency of the system.
 22. The hot water control system of claim 19, wherein the user defined preference is the cost-efficiency of the system.
 23. The hot water control system of claim 19, wherein the user defined preference is the hot water capacity of the system.
 24. The hot water control system of claim 19, wherein the user defined preference is the time of operation of the system.
 25. The hot water control system of claim 19, wherein the user may override the system completely by bypassing the controller.
 26. The hot water control system of claim 19, further comprising a processor and data storage unit, wherein the controller may monitor user behaviour and adapt to individual user preferences.
 27. The hot water control system of claim 19, further comprising a smart meter, wherein the controller has the ability to communicate with the electricity grid to monitor demand and tariffs and adjust regulation of the heat pump accordingly. 28.-29. (canceled) 